The present invention relates to a fire observation system capable of not only searching the condition of a place where a fire has broken but also remotely observing all area including the place to be observed from the viewpoint of safety and security, and by which the development of fire at all area can be observed and of which maintenance can be effectively attained.
British Pat. No. 1,478,952 discloses an electrical circuit of smoke detection device of ionization or photoelectric type wherein a switching circuit is controlled in the operation thereof by a combination of Zener diodes for converting the resistance of switching circuit to two small and large values corresponding to the voltage impressed, and an output unit is arranged to feed two large and small outputs after the resistance of threshold component is converted two small and large values by means of switching circuit.
However, even if a plurality of these conventional fire detectors arranged in all area to be observed and protected from fire serve to feed only two outputs to the central receiving device, it is impossible to observe the development of fire in the area or the safety condition of area.
The prior art could not use effectively and fully from the viewpoint of technology the feature that the electrical output unit provided with a usual fire detection device such as smoke detector of ionization or photoelectric type and temperature detector of thermistor or semiconductor type can change the output requirement thereof, namely the detected value of detector by changing the bias voltage impressed to the input terminal thereof. In addition, the prior art had no hard and soft wares necessarily enough to cause the detectors to feed searching detection information ranging from a small value to a large one as well as information assigned to each of detectors, so that the prior art was remarkably disadvantageous in that a fire observation system, which is high in reliability and preferable in maintenance, needed an extremely high cost.